Abstract
The objective of this study was to perform a structural characterization and evaluate the in vitro safety profile and in vitro antioxidant activity of liquid crystalline systems (LCS) with and without retinyl palmitate (RP). LCS containing polyether functional siloxane (PFS) as a surfactant, silicon glycol copolymer (SGC) as oil phase, and water in the ratios 30 : 25 : 45 and 40 : 50 : 10 with (OLSv = RP-loaded opaque liquid system and TLSv = RP-loaded transparent liquid system, respectively) and without (OLS and TLS, respectively) RP were studied. Samples were characterized using polarized light microscopy (PLM) and rheology analysis. In vitro safety profile was evaluated using red cell hemolysis and in vitro cytotoxicity assays. In vitro antioxidant activity was performed by the DPPH method. PLM analysis showed the presence of lamellar LCS just to TLS. Regardless of the presence of RP, the rheological studies showed the pseudoplastic behavior of the formulations. The results showed that the incorporation of RP in LCS improved the safety profile of the drug. In vitro antioxidant activity suggests that LCS presented a higher capacity to maintain the antioxidant activity of RP. PFS-based systems may be a promising platform for RP topical application for the treatment of skin aging.
Highlights
The demand for products that reduce skin aging is constantly growing because people want to stay young as long as possible
DC 5329 (S), and silicon glycol copolymer, DC 193 (O), were purchased from Dow Corning (Michigan, USA), and retinyl palmitate (RP) 1,000,000 IU/g was purchased from Roche (GreenzachWyhlen, Germany)
Two formulations were selected for tests—opaque liquid system (OLS), constituted by 30% surfactant, 25% of oil phase, and 45% of water, and transparent liquid system (TLS)—constituted by 40% PSF, 50% silicon glycol copolymer (SGC), and 10% water
Summary
The demand for products that reduce skin aging is constantly growing because people want to stay young as long as possible. Aging is a natural and inevitable process that reverses the biological characteristics acquired during development and leads to cell death [3]. Skin aging is influenced by several factors including genetic factors, environmental exposures (ultraviolet radiation (UV), xenobiotics, and stress mechanisms), hormonal changes, and metabolic processes (generation of reactive oxygen species as chemically activated sugars and aldehydes). All of these factors act together in changing the structure, function, and appearance of the skin [5]
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